linux-kernel - Re: [golang-dev] Re: mmap, the language go, problems with the linux kernel

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Message-ID: <mcrei7hnfs2.fsf@google.com>
Date:	Wed, 09 Feb 2011 11:56:13 -0800
From:	Ian Lance Taylor <iant@...gle.com>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	Martin Capitanio <m@...itanio.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	golang-dev <golang-dev@...glegroups.com>,
	Russ Cox <rsc@...ang.org>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Albert Strasheim <fullung@...il.com>
Subject: Re: [golang-dev] Re: mmap, the language go, problems with the linux kernel

"Ted Ts'o" <tytso@....edu> writes:

> Linux has interpreted it to mean "virtual address space", and in fact
> it's documented as such in the its version of the getrlimit man page.
> I'd have to agree with Linus that it's probably way too late to change
> what it means (or what Linux thinks it means, anyway).

I don't think anybody seriously expects Linux to change the meaning of
ulimit -v at this point.  Obviously Go is going to do something
different here.

However, I think it's still worth pointing out that while ulimit -v no
doubt has specialized applications, it does not do exactly what I think
most people want.  I think most people want some way to say "do not let
this program cause my machine to start thrashing."  That's what I use
ulimit -v for; if I don't, a program which accidentally allocates memory
in an endless loop starts thrashing.  But I don't actually care how much
virtual memory the program is using; what I care about is limiting the
amount of physical memory it is using, so that it doesn't take over my
machine.

I think that would be a useful feature to implement regardless of how we
feel about ulimit -v and Go.  I think we can reasonably expect more and
more programs to try to advantage of large virtual address spaces.  Lets
have a way to use them while still having a way to keep them from
thrashing.

Ian
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